obtaining parents for JOptionPanes etc (was Re: How to use actionListers
within static methods)
Fred.Swartz@gmail.com wrote:
To stay in the mainstream of GUI building, don't go down the static
path. Use the common approach of subclassing JFrame, building the GUI
in its constructor, and define main in the same class. Main should
just create an object of that class, then setVisible(true) on it. Or
do that after starting a separate thread if the GUI is complicated
enough to require that.
There's no advantage to the static approach -- basically the same
amount of memory has to be allocated anyway. Java revolves around
objects, and the big disadvantage of the static approach is that not
even one object is allocated for your class. Perhaps the static
approach works for everything, but you'll discover that you have to do
a number of things a little differently.
You want a JFrame subclass to get one object, not multiple objects.
This will also keep you in the mainstream with more useful examples.
I'm having a problem with this approach. When I construct a JOptionPane,
I don't know how to specify the parent frame correctly. In the example
below, on WinXP, if you open the MyApp5 Customer dialog, then open
another app over the top, then click MyApp5 in the tray at the bottom to
bring it to front, you don't see the modal dialog because I havent set
its parent correctly. How do I specify the parent?
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import java.awt.Dimension;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
public class MyApp5 extends JFrame implements ActionListener {
private static final long serialVersionUID = 3258412832977860659L;
public MyApp5() {
JMenu editMenu = new JMenu("Edit");
editMenu.add(makeMenuItem("Suppliers"));
editMenu.add(makeMenuItem("Customers"));
JMenuBar menuBar = new JMenuBar();
menuBar.add(editMenu);
setJMenuBar(menuBar);
}
JMenuItem makeMenuItem(String itemName) {
JMenuItem item = new JMenuItem(itemName);
item.addActionListener(this);
return item;
}
public void actionPerformed(ActionEvent e) {
String command = e.getActionCommand();
if (command == "Customers") {
MyApp5CustomerPane custPane = new MyApp5CustomerPane();
}
if (command == "Suppliers") {
//
}
// Lots more like this
}
private static void createAndShowGUI() {
JFrame frame = new MyApp5();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
int width = 600;
int height = 400;
Dimension screen = Toolkit.getDefaultToolkit().getScreenSize();
int x = (screen.width - width) / 2;
int y = (screen.height - height) / 2;
frame.setBounds(x, y, width, height);
frame.setVisible(true);
}
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
} // class MyApp5
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import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
public class MyApp5CustomerPane extends JOptionPane {
private static final long serialVersionUID = 3257571685141197368L;
private String[] columnNames = { "Name", "City" };
private Object[][] data = { { "British", "London" },
{ "Continental", "Houston" }, { "SouthWest", "Dallas" },
{ "United", "Chicago" }, { "Virgin", "London" } };
public MyApp5CustomerPane() {
JTable table = new JTable(data, columnNames);
JScrollPane scroller = new JScrollPane(table);
JPanel panel = new JPanel();
panel.add(scroller);
setMessage(panel);
setMessageType(JOptionPane.PLAIN_MESSAGE);
setOptionType(JOptionPane.OK_CANCEL_OPTION);
JDialog dialog = createDialog(new JFrame(), "Customers");
// ^^^^^^^^ problem!
dialog.setResizable(true);
dialog.setVisible(true);
}
}
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